Copolymerization of divinyl benzene and isobutylene



patented Sept. 2-, 1952 v ffUNI ED: STATES PATENT 2,609,363 COPOLYMERIZATION oFpIYIriYLi BENZENE' AND'ISOBUTYLEN'E I Lester Marshall Welch, Madison; sJj.','-zassigmjrl .to Standard Oil Development-Company;afcor poration of Delaware NoDrawin'g; Application October ZQ, 1-9485 7 i Serial No. 57,407

8 Claims {01. 26088.1)

This invention relates to copolymers of isobutylene and particularly to copolymers of isobutyleneand multiolefins of theltype of divinylbenzene such as divinyl-benzene itself and tits.

analogs, whereby the character of the obtainable polymer is sharply modified to roduce either: a superior curable polymer'or 'a-type of polymer particularly adaptedto use as a pressuresensitiveadhesive or for electrical insulation in which the property or -cold flow is markedly reduced.

ln' the' .prior 'arti it has been fo'und possible to prepare aconsiderable number of extremely valuable"copolymers of isobutylene with various of the diol'efins' and multiolefi'ns such as butadiene, isoprenadimethylbutadiene, mercene and the like, copolymers. being produced to contain multiolefin's having from 4 to' about 14 carbon atoms per molecule. It has also been foundpossible to modify the properties of such copolymers by the addition of tracesof'divinylbenzene in amounts of fromone-tenth to five parts per hundred parts'of isobutylene, with from twoto thirtyor forty-parts of the multiolefinsbeingused. All

of these polymers are, however, moreorless deficient in that they show' undesirably high propertiesof cold/flow before'curing, and'all are some what low in curing speed.

7 According to the present invention, it is found that-ta highly valuable copolymer can-be-produced from 'isobutylene and divinylbenzene or substitutedi-divinylbenzenes. By this procedure there-is obtained a 'copolymer in which the amountof cold flow is markedly less, when the material is used for the making of such materials as inner tubescor other rubber-like goods in which the material is required to have a fairamount of stiffness or mechanical strengthbefore curing. It is alsoifound that .a. polymer of. this typecontaining substantial or significant amounts from about one- 'half part of divinylbenzene per hundred of isobutylene up to five partsto ten parts or even occasionally as high asfifteen'or twenty parts per hundred of isobutylene is particularlyvaluable for usesin which it is not cured such as in pressure sensitive-coatings (Scotch tape type of structures) because of 'thegreatly reduced tendency toward .cold .fiow, and-the maintenance of a-very high adhesiveness.

Thus the present invention consists in the productionrof'a simple copolymer'of isobutylene and a divinyl-type substance. The first embodiment of the' invention utilizes isobutylene of good purity,i.preferably at least 95% purity and better, from.98% to' 99% purity. With'this there is thenmixed a suitable amo-unt of divinylbenzene, pref- 2 l erably from one-tenthv part to a-maximumof twenty parts per hundred of isobutylene.

Insteadiofdivinyl benzene anyoi the divinyl aromatic substances'may be used, including such, substances as divinyltoluene, or divinyl xylene or divinylnaphthalene, or the'like. According to, the

present'invention any compound containingone or more aromatic nucleisubstitutedby at least two vinyl radicals may-be used, provided only that any.- other substituents, present are not such as to interfere with the polymerization, or that sumc-ient steric hindranceis'presentto prevent inter fere'nce. That is, halo substituted divinyl aromaticsare as. satisfactorily usable as are the it simple divinyl benzenes.

not even appear that'it is necessary that the sub,-

stituent be fully saturated, since the substituent may'alsocontain'one ormore'carbon to carbon double linkages. j r

Thesecompounds ,areall'tobe regarded/as analogs of divinyl benzeneand are representative only since thereare many'more'ana-logo-us compounds which are equally usable.

The-resulting mixture isthen cooledtoa tem:- perature withinthe range between about '10 C., and about l00 (3., as obtainable by .the use ofvarious refrigerants, and byreducedpressures on a refrigerating jacket containing liquid ethylene, or even lower, to temperatures'obtainable bymixtures of liquid hydrocarbon refrigerants with liquid methane, even down: to 164 C.,

'atthe boiling point of liquid methane, although these latter temperatures, ibeingexpensive to obtain, are commercially undesirable. When the desired low temperature has been obtained, the material is stirred vigorously by an appropriate stirrer and then a catalyst in the form of a solution of a Friedel-Crafts type catalyst in solution in a low .freezing non-complex forming solvent or in liquid condition is then added to the cold unsaturate mixture.-

For this purpose aluminum chloride insolution in methyl chloride is the preferred catalyst but for many uses boron tri-fiuoride either in gaseous form or in solution in such solvents as liquid propane, liquid ethane, liquid ethylene or even higher boiling solvents is entirely usable. Similarly, aluminum bromide, especially in solution in a hydrocarbon, is usable as is also titanium tetrachloride and the other similar Friedel- Crafts catalysts.

Thus, for the Friedel-Crafts active methyl halide catalyst substance any of the Friedel- Crafts metals disclosed by N, O. Calloway in his article on The Friedel-Crafts Synthesis printed in the issue of Chemicals Reviews, published for the American Chemical Society at Baltimore in 1935 in volume XVII, No. 3, the article beginning on page 327, the list being particularly well shown in page 3'75 may be used.

Such catalysts as boron trifluoride and titanium tetrachloride are normally fluid at room temperature and usually sufiiciently fluid at reduced temperatures to be usable as catalysts substances directly. The other substances must be dissolved in appropriate solvents. For this solvent, it is required only that it be low freezing, thereby having a freezing point below the freezing point of water, and that it shall be non-complex forming; this requirement being that there shall not separate out from solution on evaporation of the solvent a compound between the solvent and the Friedel-Crafts catalysts; or that the boiling point of the solvent shall be lowered by only a small amount from its normal boiling point by the presence of the solvent; or as pointed out by Findley in The Phase Rule and Its Application, 6th edition, Longmans, Green and Company, New York, the solvent to be non-complex forming must permit of the addition of the solvent in the form of a vapor to the catalyst at constant temperature and when so added lead to a substantially continuous change in the composition of the catalyst phase and to a continuous increase in the partial pressure of the solvent. In general the catalyst can be recovered unchanged by removal of the solvent.

There may also be present in the olymerization reaction a suitable diluent which may take the form of any of the normal halo substituted aliphatic compounds such as ethyl or methyl chloride, ethyl or methyl dichloride, chloroform, ethylene tetrachloride or the like. For this purpose any of the halo substituted alkyl compounds which are liquid at the polymerization temperature are more or less satisfactory. Alternately also, such substances as carbon disulfide or the petroleum hydrocarbons may be used as diluents. It is found that the presence of the diluents is markedly helpful in that it reduces and minimizes the amount of cross linkage formed and reduces the amount of hydrocarbon insoluble polymer produced.

It may be noted that the amount of divinyl compound copolymerized from any given mixture is a function of the relative copolymerizability of the isobutylene and the divinyl compound present. These compounds are less troublesome than such diolefins as butadiene, in that they tend to copolymerize more nearly in the proportion in which they are present in the mixture. However, some show a markedly higher copolymerizability rate and some show a distinctly lower copolymerizability rate, and accordingly, there is no necessary connection between the proportion of divinyl compound in the polymer and the amount in the polymerizate feed.

It is found, however, that the presence of divinyl benzene tends rather strongly to the production of insoluble gel material which interferes with subsequent processing. This material can be removed by dissolving the polymer in hydrocarbon solvent and filtering the solution, preferably in the presence of an appropriate filter aid, such as an infusorial earth, or the like, but in any event, it is found that the proportion of .divinyl benzene in the finished polymer should be kept below about 2% to 3% or about 20% in the feed since higher values strongly tend to the production of gel, both in the polymerizer, and during subsequent processing.

Low values of insoluble gel polymer can also be obtained by including small amounts of the normal butenes in the polymerizate mixture. It does not appear that the normal butenes interpolymerize, but they do exert a profound effect on the polymerization, reducing both the amount of gel polymer and the obtainable molecular weight.

The resulting polymer usually is a white plastic solid, depending to some extent upon the presence of impurities, to some extent upon the temperature of polymerization, and to some extent upon the temperature of polymerization as well as upon the particular catalyst used. The polymer obtained may show an iodine number ranging from about 0.4 up to amounts as high as about 50. Polymer having the molecular weight of above about 20,000 is still somewhat plastic but with only small amounts of cold flow. Thus if the molecular weight is above about 20,000, and the iodine number above from 0.4 to l, the polymer shows the valuable property of a curing reaction with such substances as sulfur or with paraquinone dioxeme and its homologs or with the various dinitroso compounds to yield a cured polymer substance having a definite tensile strength and a definite elongation at break, which is an excellent substitute for or replacement for caoutchouc. When so cured, tensile strengths ranging from 500 lbs. per square inch up to 3500 or even 400 lbs. per square inch are obtainable, with elongations atbreak ranging from 250% up to 1200%, depending upon the degree of cure and the type and amount of fillers and other additives present.v This polymer, capable of curing, shows the very valuable property of almost complete absence of cold flow before curing thereby greatly simplifying the preparation of inner tubes wire insulation and other rubber-substitute structures.-

Alternatively, and within the scope of the invention, by the use of temperatures Within the range between about 10 C. and about -40 C., with the less potent .catalyst and less pure .reactants, copolymers ranging from molecular weights in the order of 1000 to 20,000 are obtainable. Copolymers within this molecular weight range do not cure to a solid, substance having a definite tensile strength and definite elongation at break. They are, however, extremely valuable. for many purposes such as for the production of cements. Copolymers with a molecular weight ranging from 5000 to about 15,000, either as such,

or in combination with a wide range of other sub stances, such as rubber, thermoplastic resins and plasticizers, may be used for highly valuable pressure sensitive materials which show a minimum of cold fiow and a maximum tackiness and a maximum firmness of holding of the pressure sensitive coated sheet to the desired object. The above indicated top of 15,000 molecular weight is ride.

not, :however, a limiting value;v since it is. found thatxpolymers having. molecular weights as high as 35,000 .or. even 40,000 are desirable-for some forms of adhesives, especiallywhen' they are modified'by small amounts of softenerssuch as the fluid hydrocarbons or by simple -polybutenes,'or by broken-down rubber, or the like. a

Thus it "will be observed that. the .copolymer of the present invention has various widelyfiifferent items of utility,'depending inpart .on-the molecu- 1ar-weight,. in part on theipresence of associated compounds and in part on theparticularuse desired.

EXAMPLET Two mixtures of isobutylene withdivinylbenzene were; prepared as shown in the subjoined Table ltogether-with appropriate amounts of diluent. The first of these mi;xtures.contained 350 parts of isobutylene, 10. parts of divinylbenzene, and'1050 parts of methyl chloride whereas the second mixture was the same except for the useof 20 parts of divinylbenzene. These mixtures were cooled to a temperature of approxi mate1y-. 98 C., by the use of a jacket of liquid ethylene on the reactor, and were then polymer-s ized by the addition of an appropriate catalyst 7 consisting of a solution of approximately 26 parts ofaluminumchloride per 100 cc., of methyl chlostirred and the catalyst solution added inasmall highpressure jet into thebodyof the strongly stirred mixture of unsaturat e-andl diluent. The

polymerization reaction proceeded rapidly and it was found that each gram of aluminum chloride in the catalyst would produce approximately 220 grams of solid polymer. As shown in the table, the respective polymers showed molecular weights of 34,200 and 42,200 and iodine'numbers respectively of 2.0 and 3.5. 1

These polymers were removed from the polymerization mixture, brought up to room tempera;- ture, washed on the double roll millwith waterto remove residual volatiles and catalysts, and then were compounded according to the following recipe and cured.

Parts Copolymer 100 Stearic acid 5 Zinc oxide 5 Carbon black 10 Sulfur 3 Tetra-methyl thiuram disulfide 1 The resulting compounds were then cured for 8, 16 and 32 minutes in each instance and tensile strength, elongation and modulus determined the yield the values shown in the subjoined Table I.

The unsaturate mixture was; vigorously This table shows the 7 production of an excel-= lent copolymer; suitable --as a 7 very v valuable replacement for natural rubber whichis particularly suitable for tires, tubes; for proofed goods,

and for such goods as rubber gloves andother dipped goods? and wire insulation.

- "A series of polymerizations were madein whichthe divinylbenzene concentration in the fee rangedfrom' 0.1 weight percent to 0.8 weight percent, based onisobutylene. A temperatureof l00 C. was maintained in the reactor by using liquid ethylene as the internalrefrigerant to the extent of 3 volumesof ethylene toone volume of' isobutyl'ene. Tothis; mixture there was a then added 10% of butene-l based onthe isob'utylene present in the feed to modify the polymer-by re ducing molecular weight and increasing its solubilit'y. The' polymerization was carriedout by I adding acatalystsolution consisting of 0.38 gm.

A1013 per 100 cc. of methyl-chloride. The-following data were obtained: if

'7 I I I Percent Flow P g P cent Mooney Percent Gel C. 1.8 3. 2 212 F. in .Polymer.-Kg/sq.'cm..

., 7 Ior iweeks- -;'0.0 80 do I "37 0:1 69 8.3

40 a 64 21.4 0 0.4 at 79 54.0 0 Q 0. 6 -7]. 58 41'. 2 0 0.8 55 42.9 5

It is apparent from the above table that as little as 0.1% DVB in the feed greatly reduces the tendency of the polymer to flow.

This material thus is highly satisfactory for use as a pressure sensitive material in the making of Scotch tape type of material.

EXAMPLE III In order to reduce el content of the polymers and also to lower the Mooney viscosity or molecular weight of the polymers, the butene-l Table I [Divinylbenzeue (D. V. B.) and isobutylene copolymerizationJ] Feed T Catalyst 1 emper- Run I b 1etlure of lzercen t ggg Iodine N so uo ymeronv.

MeCl D. V. B. Oonc. Eff. Wei ht cc. gz cc. anon g./l00 cc. g.pol./g.cat. g

1 Polymerizations were conducted in a 2.5 liter refrigerant jacketed batch reactor.

3 Based on isobutylene.

7. content of the feed was increased to 20 weight percent based on isobutylene and other conditions were maintained the same as given in Example II:

The gel content of the above polymerswas low when the DVB concentration in the feed was below 0.8%.

Thus the present invention produces a new copolymer consisting of a copolymer of isobutylene and a divinyl'aromatic compound which within the respectivemolecular weight ranges is an excellent substitute for or replacement for natural rubber and;an excellent substitute for previously used pressure sensitive coatings. a

While there are above disclosed but a limited number of embodiments of the invention, it is possible to produce still other embodiments without departing from the inventive concept herein disclosed and it istherefore desired that only such limitations be imposed upon the appended claims as are stated therein or required by the prior art.

What'is claimed is:

1; A copolymer of a major proportion of isobutylene with a minor proportion of a diviny1 aromatic compound, there being no more than two carbon atoms present in each vinyl substituent on the aromatic nucleus and said copolymer having a molecular weight within the range between 1,000 and 100,000, the isobutylene being present in the reactant feed used for preparing the copolymer in the amount of at least 97%, and the diviny1 aromatic compound being present in the reactant feed in an amount within the range between 0.1% and 0.8% and there being about 10 to 20% of l-butene present in the 81 reactant feed mixture; the copolymer having a minimumof' cold flow and being characterized by. the property of surface pressure sensitivity.

2. A copolymer such as that described in claim 1 in which the diviny1 aromatic compound is diviny1 benzene.

3. A copolymer such asv that described in claim .1 in which the diviny1 aromatic compound is diviny1 toluene.

4. A copolymer such as that described in claim 1 in which the diviny1 aromatic compound is diviny1 naphthalene.

5. A polymerization process comprising the steps of mixing together a major portion of isobutylene, 0.1 to 0.8% of a diviny1 aromatic compound having no more than two carbon atoms present in each vinyl substituent on the arcmatic nucleus and from 10 to 20% of butene-l based on the isobutylene, cooling the resulting mixture toa temperature within the range between 10" C. and '164 C'. and polymerizing the mixture by the application thereto of a Friedel-Crafts'active metal halide catalyst in solution in a low freezing, non-complex-forming solvent.

' 6. A copolymer such as that described in claim 5 in which the diviny1 aromatic compound 7 is diviny1 benzene.

'7. A copolymer such as that described in claim 5 in which the diviny1 aromatic compound is diviny1 toluene.

8. A copolymer such as that described in claim 5 in which the diviny1 aromatic compound is diviny1 naphthalene.

' 1 LESTER MARSHALL WELCH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,213,423 Wiezevich Sept. 3, 1940 2,274,749 Smyers Mar. 3, 1942 2363538 Gleason et a1 Jan. 30, 1945 

1. A COPOLYMER OF A MAJOR PROPORTION OF ISOBUTYLENE WITH A MINOR PROPORTION OF A DIVINYL AROMATIC COMPOUND, THERE BEING NO MORE THAN TWO CARBON ATOMS PRESENT IN EACH VINYL SUBSTITUENT ON THE AROMATIC NUCLEUS AND SAID COPOLYMER HAVING A MOLECULAR WEIGHT WITHIN THE RANGE BETWEEN 1,000 AND 100,000, THE ISOBUTYLENE BEING PRESENT IN THE REACTANT FEED USED FOR PREPARING THE COPOLYMER IN THE AMOUNT OF AT LEAST 97%, AND THE DIVINYL AROMATIC COMPOUND BEING PRESENT IN THE REACTANT FEED IN AN AMOUNT WITHIN THE RANGE BETWEEN 0.1% AND 0.8% AND THERE BEING ABOUT 10 TO 20% OF 1-BUTENE PRESENT IN THE REACTANT FEED MIXTURE, THE COPOLYMER HAVING A MINIMUM OF COLD FLOW AND BEING CHARACTERIZED BY THE PROPERTY OF SURFACE PRESSURE SENSITIVITY. 